Solid solutions of double phosphate hexahydrates in the MgNH4PO4 • 6H2O-Ni2+-H2O system and their dehydration products

Substitutional solid solutions Mg2+ a dagger Ni2+ of crystal hydrates Mg(1 - x)Ni (x) NH4PO4 center dot 6H(2)O and Mg(1 - x)Ni (x) NH4PO4 center dot H2O (where 0 < x a parts per thousand currency sign 0.65), which have struvite structure and dittmarite structure, respectively, have been studied. Ion exchange Mg2+ a dagger Ni2+ influences the condition of M2+-H2O (M2+ = Mg2+, Ni2+) coordination bonds and hydrogen bonds involving coordinated H2O molecules, as probed by X-ray powder diffraction, thermal analysis, and FTIR spectroscopy. The coordination of water molecules to metal ions in those crystal hydrates is treated to be a factor that determines the propensity of the resulting crystal structures to polymorphism.